In a communications system, data transmission reliability is usually improved by means of channel encoding, to ensure communication quality. A polar code is a linear block code, and it has been theoretically proven that the polar code is an encoding manner that can achieve a Shannon capacity and has low coding-decoding complexity. Encoding an output of a polar code may be represented as follows:x1N=u1NGN.,
where u1N={u1, u2, . . . , uN} is a binary row vector having a length of N; and GN. is an N*N matrix, and GN.=BNF⊗n, where a code length N=2, n≥0,
      F    =          [                                    1                                0                                                1                                1                              ]        ,BN is a transposed matrix, and F⊗n is a kronecker power (kronecker power), where it is defined that F⊗n=F⊗F⊗(n-1).
In an encoding process of a polar code, some bits in u1N are used to carry information, where these bits are referred to as information bits, and it is assumed that a set of indices of these bits is A; and other bits are fixed values, referred to as frozen bits, and are usually set to 0. Therefore, encoding output of a polar code may be simplified into x1N=uAGN.(A), where uA is a set of the information bits in u1N, and uA is a row vector having a length of K, where K is a quantity of the information bits; GN.(A) is a sub-matrix, in GN., obtained according to rows corresponding to indices in the set A, and GN.(A) is a K*N matrix; and performance of the polar code depends on selection of the set A.
To match a bearer capability of a physical channel and reach, during channel mapping, a bit rate required by a transport format, rate matching further needs to be performed on a polar code. In the prior art, a traditional HARQ (Hybrid Automatic Repeat Request) technology for random (quasi-random) puncturing is used for a polar code, that is, a puncturing location is randomly (quasi-randomly) selected. The prior art has a high frame error rate and poor HARQ performance.